Deflecting device for braun tubes



Marth 28,1939. E. RU'SKA 2,152,363

DEFLECTING DEVICE FOR BRAUN TUBES Filed Dec. 6, 1935 I ye/260:

Patented Mar. 28, 1939 v, 7

DEFLECTING-DEVICE FOR BRAUN TUBES Ernst. Ruska, Berlin-Zehlendorf, Germany, assignor to the firm; of Fernseh Aktiengesellschaft, Zehlendo'rf; near Berlin, Germany Application December 6, 1935, Serial No. 53,264 In Germany December 12, 1934 4 Claims. (Cl. 250-159) This invention relates to-deflecting plates for not the line or point spacing over the picture, Braun tubes. measured along the curved fluorescent screen, To increase sensitivity it is known to curve that is to be constant but the projectionthereof the deflecting plates of Braun tubes in the lonupon the plane extending perpendicularly to the 5 gitudinal direction thereof or in the direction of axis of the tube. Quantitatively, conditions are 5 the undeflected ray, so that the electrons of the such that practically in the mos-t important inbundle to be deflected entering at the edge of stances the radius of the screen is equal to or a deflecting plate flow along the curve of the greater than the distance of the deflecting sysplate at maximum deflecting tension. term from the screen. The deflecting sensitivity is According to the invention, whether parallel, must then decrease outwardly in order to proin inclined or curved, the plates are curved along duce points or lines of uniform relative spacing their breadth, i. e., transversely to the direction on the screen and particularly on the plane disof the ray, in such a way that the two plates posed vertically to the axis of the tube. The forming a pair have a concave or convex form deviation from the constancy of sensitivity due 5 relative to the ray. to the geometrical conditions in wide angle de- The first result of this construction with reflecting systems mitigates therefore the effect spect to pairs of plates on which the undeflected of a not strictly linear saw-tooth voltage upon ray falls and which form the first deflecting systhe image geometry, as the increase thereof in tem is a local sensitiveness varying somewhat time decreases somewhat with the voltage.

with the deflection. This due to the fact that The radius of curvature is selected according 20 in the planes disposed vertically tothe ray the to the relative plate distance and the voltage lines of force do not extend parallel any more to be compensated or the geometrical conditions, but, owing to vertical emergence from both though it need not be constant over the plate plates, either bulge in the middle plane or conlength. It is frequently preferable to refrain verge, according to the curvature of the plates. from curving the entrance edge of, the plate 5 The deflected ray passes through a stronger or system and to increase the curvature only graduweaker transverse field than the undeflected ray ally towards the outlet edge. This is particularly in the center. Only at the plate entrance the necessary in case of plates upon which the ray cross section of, the ray simultaneously extends is incident While it is still undeflected and if the over the middle and marginal field if the disspacing of the entering edges corresponds to the 30 tance of the plate entrance is equal to the diamediameter of the ray. ter of the ray at this point. Due to the bulging By Way of example, the invention is diagram; of the lines of force, the local sensitiveness of matically illustrated in the accompanying drawplates that are convex relative to the ray is ing, in which Figures 1, 2, and 3 are plan, vertical slightly lower when the ray is at rest than in case and end views respectively of one pair of deflect- 35 of a deflected ray, whereas concave plates ining plates.

versely disclose a somewhat lower marginal Figures'4, 5 and 6 are plan, vertical and end sensitive-ness. views of. a second pair of deflecting plates.

Such intentional variation in sensitiveness is Figure 7 is a view of a cathode ray tube in 40 required chiefly for two reasons. section with both pairs of deflecting platesposi- 40 In the first place, variation in sensitivity of tioned therein. this kind permits compensation of the usually Referring to the drawing, and first to Fig. 1, a

not strictly linear saw-tooth voltage with repair of deflecting plates referred to in the prespect to deflection. Since sweep circuits are ceding last paragraph of the general description much cheaper and simpler if strict linearity can is designated l, 2. The strength of the trans 45. be dispensed with and lateral curving of the verse field is to be as constant as possible over plates practically does not involve extra expenthe ray section itself. When deflected the ray diture, an essential technical advantage is comes out of central position. only in the course gained. I of the plate length and, without too much vari- A further reason for lateral curving of the ation in the field strength over the'ray section, 50 plates to insure very wide-angled deflection, passes according tothe amount of its deflection which is desirable with respect to short tube through flelds of varying intensity, whereby varilength, is that the geometrical conditions alone ation in sensitivity is insured. demand a somewhat variable angular sensitivity A second and different variation in sensitivity (angular deflection: deflecting voltage). It is with respect to plates curved along their broad- 55 in sensitivity is particularly necessary in the wide angle first deflecting system and usually consists in keeping constant the sensitivity relative to the course thereof which in non-curved plates is determined by the beam paths differing in length according to the angle of incidence.

It is advisable to form the plates of such a pair as sectors of a surface of rotation with the plates inclined, e. g., from a cone surface. Figs. 4, and 6 show such sectors designated 3, 4 the cones of which lie with their axes vertically to the axis of the ray, the limitation of the plates on the entering side being formed by the intersection of a plane parallel to the axis of the tube with the cone. The axis of the cone preferably extends through the pivot of the first deflecting system, so that the radius of the intersection is equal to the distance of. the entering edge from the pivot of the first deflecting system. The leaving edge also develops as intersection of a parallel plane with the sector of the cone surface. The advantage afforded by such plates is that the ray always enters and leaves vertically to the edge of the plate. A section.AB in a plane vertically to the direction of the ray shows in Fig. 6 the curvature of the plate.

If plate-like electrodes are used besides the deflecting plates proper, they are also preferably formed from corresponding surfaces of rotation, the projection thereof ensuing as continuation to the undeflected ray axis of said tube as defined by cross-sectional planes perpendicular to said axis.

2. In a cathode ray tube, an electrostatic ray deflecting device, consisting of two deflecting plates having opposed convex curvatures of different radii of curvature relative to the undeflected ray axis of said tube as defined by crosssectional planes perpendicular to saidaxis.

3. An electron beam deflecting device for a cathode ray tube, comprising plates having each a convex curvature relative to: the undeviated cathode ray axis of said tube, as defined by crosssectional planes perpendicular to said axis, said plates having a changing radius of curvature along their length.

4. An electrostatic ray deflecting device for a cathode ray tube having therein cathode ray beam producing means, consisting of two deflecting plates of opposed convex curvature relative to the undeflected ray axis of said tube in a plane perpendicular tosaid axis, said plates having straight edges on the side thereof toward said beam producing means.

. ERNST RUSKA. 

